The connection between abnormal protein phosphorylation and the cause or consequence of diseases has been known for over 20 years. Accordingly, protein kinases have become a very important group of drug targets. [See Cohen, Nature, 1:309-315 (2002), Gaestel et al. Curr. Med. Chem. 14: 2214-223 (2007); Grimminger et al. Nat. Rev. Drug Disc. 9(12):956-970 (2010)]. Various protein kinase inhibitors have been used clinically in the treatment of a wide variety of diseases, such as cancer and chronic inflammatory diseases, including rheumatoid arthritis and psoriasis. [See Cohen, Eur. J. Biochem., 268:5001-5010 (2001); Protein Kinase Inhibitors for the Treatment of Disease: The Promise and the Problems, Handbook of Experimental Pharmacology, Springer Berlin Heidelberg, 167 (2005)].
JNK is a ubiquitously expressed serine/threonine kinase belonging, together with ERK (extracellular-regulated kinase) and p38, to the family of mitogen-activated protein kinases (MAPKs). [Kyriakis J M, Sci. STKE (48):pel (2000); Whitmarsh A J, et al. Sci. STKE (1):pel (1999); Schramek H, News Physiol. Sci. 17:62-7 (2002); Ichijo H, Oncogene 18(45):6087-93 (1999)]. MAPKs are important mediators of signal transduction from the cell surface to the nucleus, using phosphorylation cascades to generate a coordinated response by a cell to an external stimulus by phosphorylation of selected intracellular proteins, including transcription factors. Additionally, JNK also phosphorylates non-nuclear proteins, for example, IRS-1, and Bcl-2 family members. [Davis R J, Trends Biochem. Sci. 9(11):470-473 (1994); Seger R et al., FASEB J.; 9(9):726-35 (1995); Fanger G R et al., Curr. Opin. Genet. Dev.; 7(1):67-74 (1997)].
The mitogen activated protein (MAP) kinases participate in the transduction of signals to the nucleus of the cell in response to extracellular stimuli. Examples of MAP kinases from the ERK p38 and JNK isoforms include but are not limited to, mitogen-activated protein kinase 1 (ERK2), mitogen-activated protein kinase 8 (JNK1), mitogen-activated protein kinase 9 (MAPK9 or JNK2), mitogen-activated protein kinase 10 (MAPK10 or JNK3) and mitogen-activated protein kinase 14 (MAPK14 or p38alpha). MAP kinases are a family of proline-directed serine/threonine kinases that mediate signal transduction from extracellular receptors or heat shock, osmotic stress, reactive oxidant species (ROS) or UV radiation. [See Sridhar et al., Pharmaceutical Research, 17:11 1345-1353 (2000)]. MAP kinases are activated via the phosphorylation of theonine and tyrosine by upstream dual-specificity protein kinases, including MKK and MEKK kinases. Cell proliferation and differentiation have been shown to be under the regulatory control of multiple MAP kinase cascades. [See Sridhar et al., Pharmaceutical Research, 17:11 1345-1353 (2000)]. As such, the MAP kinase pathway plays critical roles in a number of disease states. For example, defects in activities of MAP kinases have been shown to lead to aberrant cell proliferation and carcinogenesis. [See Hu et al., Cell Growth Differ. 11:191-200 (2000); and Das et al., Breast Cancer Res. Treat. 40:141 (1996)]. Moreover, MAP kinase activity has also been implicated in insulin resistance associated with type-2 diabetes [See Virkamaki et al., J. Clin. Invest. 103:931-943 (1999)] and obesity. Changes in insulin resistance may have a direct impact on the metabolism of glucose and lipid in the liver contributing to the development of steatosis that may progress to liver fibrosis [Vallerie et al. Science Translational Medicine 2(60):1-7 (2010)].
Steatosis may develop in the presence of either saturated or unsaturated free fatty acids (FFA). FFA promote robust JNK activation in liver and excessive concentrations of FFA may lead to hepatocyte apoptosis. It has been reported that JNK2−/− mice are partially protected from steatosis and apoptosis by saturated FFA (e.g. stearic acid) but not by unsaturated FFA [Malhi et al. J. Biol. Chem. 281:12093-12101 (2006)]. JNK1−/− mice were not protected from FFA induced injury. The role of JNK1 and JNK2 has been studied in CDAA-fed mice that progressed from steatosis to steatohepatitis to hepatic fibrosis [Kodama et al., Gastroenterology 137:1467-1477 (2009)]. While both JNK1−/− and JNK2−/− mice developed steatosis, the JNK1−/− mice, but not JNK2−/− mice, were remarkably resistant to progression to hepatitis and fibrosis. Chimeric mice with JNK1−/− deletion restricted to bone marrow cells were similarly resistant to hepatitis and fibrosis implicating the activated Kupffer cell as a key trigger for disease progression beyond steatosis. Indeed, JNK1−/− macrophages do not express IL-1, IL-6, TNF and NO in response to LPS [Sanchez-Tillo et al., J. Biol Chem. 282(17):12566-73 (2007)], and Kupffer cells derived from JNK1−/− mice or from wild-type mice and treated with JNK inhibitor SP600125 display reduced TNF, IL-6, and IL-1 expression in response to LPS [Kodama et al., Gastroenterology 137:1467-1477 (2009)].
The elucidation of the intricacy of protein kinase pathways and the complexity of the relationship and interaction among and between the various protein kinases and kinase pathways highlights the importance of developing pharmaceutical agents capable of acting as protein kinase modulators, regulators or inhibitors that have beneficial activity on multiple kinases or multiple kinase pathways. Accordingly, there remains a need for new kinase modulators, and in particular JNK modulators.
Citation or identification of any reference in Section 2 of this application is not to be construed as an admission that the reference is prior art to the present application.